The challenge to minimizing or eliminating deck cracking is the contradiction between the flexibility needed to accommodate shrinkage strains and the stiffness/bonding required to provide full composite action. It is possible to achieve both of these contradicting goals through the use of controlled composite action (C2A) connectors for the deck-girder system. The innovative design mechanism controls composite action by preventing it during early ages (i.e., to allow for unrestraint crack free concrete shrinkage) while it is activated for higher service load and under ultimate loadingcondition. To achieve this objective (i.e., no composite action initiallyand full composite action ultimately) it is proposed that the shear connectors be wrapped in a hyper-elastic (rubber like) material of carefully designed thickness. Under low level of stresses the hyper-elastic material does not provide any resistance and deforms easily allowing for unrestraintshrinkage of concrete deck. Subsequent to initial straining due to shrinkage, the hyper-elastic material will develop high level of resistance and will fully engage the shear studs, thus, providing full composite action. This paper describes the design concept and provides preliminary results from a proof-of-concept project.
Abstract